JAKARTA, Oct. 28 (Xinhua) -- Chief executive of Indonesian airlines Lion Air said Monday that cracks have been found in two of the airlines' Boeing 737 NG (Next Generation) fleet, adding the number of similar planes serving domestic airlines with crack findings.

"We already did the checking procedures. Our Boeing 737 NG fleet comprised of 90 ones, but the cracks were only found in two of them," Lion Air Group President Director Edward Sirait said.

Indonesian transportation ministry in mid October grounded the operation of three Boeing 737 NG planes operated by state-run Garuda Indonesia Airways and private airlines Sriwijaya Air over the findings of cracks in the planes' air frames.

Grounding on those planes would continue until further recommendations issued by Boeing, the ministry said.

To address the flight safety, Edward Sirait assured that repair procedures would be conducted over those planes. But he did not make it clear whether those planes were still operating.

"Repairing works will certainly be conducted over those planes. If those planes are grounded, and the repairing is yet to be done, we will continue ground them. But if the repairing works are done and they are declared fit to fly, we will fly them," he said.

The grounding order was issued after inspections carried out by the transportation ministry to follow suit airworthiness directives issued by international aviation agencies to check the Boeing 737 NG planes with over 30,000 Flight Cycle Number (FCN) operated by all airlines in the world.

The ministry has also advised all domestic airlines, including Garuda Indonesia, Sriwijaya Air, Lion Air and Batik Air, to check airworthiness of their Boeing 737 NG planes and carrying out periodical maintenance every 3,500 FCN over the planes as well.